The invention pertains to the treatment of wastewater to remove pollutants. More specifically, the invention provides method and apparatus for the physical treatment of wastewater to remove particulate matter and biological treatment for the removal of organic material. The present invention employs rotating partially submerged biological contactors to grow aerobic biological slimes for the oxidation of organic pollutants and settling zones subjacent to the contactors for removal of both the raw primary and secondary solids generated by the biological treatment from the wastewater.
U.S. Pat. No. 3,575,849 issued to Torpey discloses a method and apparatus for biologically treating wastewater including a treatment tank having a biological treatment zone in its upper portion and a quiescent settling zone in its lower portion. The biological treatment zone includes a plurality of parallel rotatable shafts disposed across the upper portion of the tank; each of the shafts supporting a plurality of biological contactors, typically thin discs. The contactors extend into the wastewater in the tank to less than half the tank depth, providing a subjacent settling zone for sloughed off solids. The surface of the biological contactors is alternately exposed to the atmosphere and immersed in the wastewater at suitable intervals to promote the growth of aerobic biological slimes.
The U.S. Pat. No. 3,776,841 issued Dec. 4, 1973 to Torpey, discloses a wastewater treatment tank having an upper biological treatment zone including rotating partially submerged contactors to grow aerobic biological slimes and a subjacent settling zone. The subjacent settling zone is physically separated from the biological treatment zone by a false bottom or longitudinal baffle. Wastewater is introduced into the upper biological treatment zone, flows through the upper zone, around the longitudinal baffle and into and through the subjacent settling zone to a treated wastewater outlet.
The U.S. Pat. No. 3,563,383 to Hellquist, pertains to a method for treating organically polluted wastewater including biological treatment using partially submerged contactors in the upper portion of a section of the treatment unit. The Hellquist system separates primary from secondary treatment as it utilizes a plurality of separate bays arranged in series for primary settling before the wastewater enters the biological treatment section.